1. Field of the Invention
The invention relates to a method for cleaning coke oven gas by washing the gas, whereby a washing liquid is guided into a washing liquid circuit and impurities in said washing liquid are expelled in a desorber. Such a method is known from Cheme-Ingenieur-Technik [Chemical Engineer Technology](1974) 15, page 628.
2. The Prior Art
In the known method, washing the gas takes place with a washing liquid that contains ammonia, which causes ammonia to become concentrated in the washing liquid circuit between the gas washer and the desorber. Ahead of the desorber, caustic soda is put into the washing liquid circuit, in order to split non-strippable ammonium salts into ammonia and NaCl. The desorption process is carried out in two stages. In a first desorption stage, the acid gas components are expelled from the charged washing liquid. A partial stream of the liquid stream drawn off from the desorber is passed to a second desorber, in which ammonia is expelled with steam. The ammonia expelled here is passed back to the washing liquid circuit. The two-stage desorption process is complicated, in terms of process technology and control technology, since on the one hand, the aim is to completely remove the acid gas components and, at the same time, a sufficient amount of ammonia must remain in the washing liquid circuit.